In the production process for semiconductor devices, a cleaning process of cleaning a semiconductor wafer (hereinafter referred to as “wafer”) with process solutions such as a chemical liquid and a rinse liquid is conducted. In such a cleaning process, after performing a chemical liquid processing step that supplies a chemical liquid such as DHF (diluted hydrofluoric acid) solution to the wafer and a rinsing step that supplies a rinse liquid such as deionized water to the wafer, a drying step for drying the wafer is performed.
As one example of a method of drying the wafer, a vapor drying method that exposes the wafer to a vapor of an organic solvent such as IPA (isopropyl alcohol) has been known. Further, in order to suppress generation of water marks during a drying step, a method of supplying dehumidified air thereby to lower the ambient humidity around the wafer has been proposed (for example, refer to Japanese Utility Model Laid Open Publication: JP 6-9130U).
In order to reduce the ambient humidity around the wafer, a great amount of dehumidified air has to be supplied. This increases the cost requiring for the processing of the wafer. In particular, in a case where a substrate processing apparatus conducts a processing step selected from several types of processing steps in one processing chamber (processing space) or in a case where the substrate processing apparatus conducts plural types of processing steps continuously, lowering of the ambient humidity around the wafer in all the processing steps results in remarkable increase in the processing cost.